The overall goal of this 3-year project is to improve the outcome of a ?marrow stimulation? procedure for cartilage repair (viz., ?microfracture?) through the use of: 1) extracorporeal shock wave (ESW) treatment to enhance marrow stimulation; and 2) an injectable hyaluronic acid-gelatin (HA-Gtn) matrix to initially contain the fibrin clot and cells infiltrating the defect from the stimulated subchondral bone marrow. This proposal is based on the prior findings in which ESWs have been found to substantially enhance the critical processes underlying the success of microfracture: neovascularization and the stimulation of MSCs. The principal objective of this study is to investigate the effects of ESWs in enhancing the outcome of microfracture for cartilage repair in a goat model, for 2 select doses of SWs. A 2nd objective is to determine if there is a benefit to injecting into the microfracture-treated defects an absorbable Gtn matrix, with and without ESW treatment. A 3rd objective is to determine the change with time in the distribution of two basement membrane proteins, laminin and type IV collagen, recently described in articular cartilage. A 4th objective is to correlate the mechanical properties of reparative tissue in microfracture-treated sites with the types of tissues comprising the reparative material, 12 month after treatment. A total of 66 adult goats will be used in the study, allocated to 11 groups of 6 animals each. Two cylindrical full-thickness chondral defects will be produced in the articular cartilage in the patella groove of distal femur of the left stifle (knee) joint of each animal, and all defects will receive microfracture. The proximal and distal defects of the left knee joint of each animal will receive the same treatment and the results from the 2 defects averaged for the statistical analysis. There will be 3 variables investigated: ESW treatment (0, SW1 and SW2); the presence or absence of a Gtn matrix; and survival time (2 wks, and 3 and 12 months). The defects in all groups will be allocated for histomorphometric evaluation. An additional group of animals will be included to generate samples for mechanical testing 12 months postoperative. The right knee joints will all undergo sham operation and serve as controls.